The present invention relates in general to the new data communication scheme specified in the IEEE 802.4 token bus specification for local area networks. More particularly the present invention relates to a circuit and method for the demodulation of signals transmitted under such communication scheme in order to obtain both the clock signal associated therewith and the data contained in such signal.
There are prior art demodulation techniques and circuits which are used with the Ethernet (IEEE 802.3) communication scheme, however these are not suitable for use with the new data communications scheme specified in IEEE 802.4. Most of the prior art demodulation methods are not only not designed for use with this new communication scheme but involve some form of sampling of the amplitude of the signal in question in order to accomplish the demodulation. Even those methods which are implemented digitally by taking a single or multiple samples of data during a bit time are subject to errors which can occur due to the presence of noise during the time the sample is taken.